Advice on motor - '47 Dodge Sedan

[rayosequis]

I am debating which way to go with the motor in my '47 Dodge sedan, as the original flat head doesn't have any compression on two of the cylinders. The motor turns over well and has seems to have some decent compression on the other cylinders.

My debate is how much effort to put into the flat head. Should I pull the head, and see if I can get it running as is or just pull the whole motor ? If I go through all the effort, it would seem unwise to not rebuild it, but then I have to look at how much money I am willing to tie up in a 65 year old motor.

I am not looking to do an all out show car or full restoration, just a cool old driver quality cruiser. So, whether the motor/tranny is original does not really matter.

An old hot rod buddy of my brothers told me the best thing to do would be to pull out the whole drivetrain and drop in a V8 and matching drivetrain to go with it. My only concern here is all the firewall and floorboard work that a swap like this entails.

Are there any other later model motor/tranny combos that would drop in without having to re-make the firewall and floor pans ?

Any advice is appreciated.

-Ernie

[Young Ed]

Your lack of compression is probably something simple. Are they adjoining cylinders? Could be as simple as a head gasket. Otherwise sticking valves is the most other likely culprit. Both can be fixed with the block in the car.

[greg g]

No compression on two cylinders usually reflects two items.

If the low cylinder are a matched pair like 1 and 2, 3 and 4, or 5 and 6, this usually indicates a bad head gasket. The pairs of cylinders are siamesed with a very thin casting between the ccylinder walls. Head gaskets typically fail at the point allowing the piston to share compression with their neighbor instead of building it.

If the low cylinders are ot members of the matched pairs, the problem usually indicated valve stuck in the open position from sitting on the high point of the cam. This is especially apparent after the vehicle has been sitting inactive for a while.

I assume you did a compression test, and that you did it both dry and wet and the wet test did not show an improvement of the low cylinders. That procedure usually tests for bad rings and the added oil helps to seal the piston temporarily.

The head gasket and the stuck valves are easy fixes, as the cylinder head on these engines usually comes off with out a lot of drama.

Pulling the head will quickly show you what is causing the low cylinders.

stuck valves can be addressed by playing whack a mole with a rubber mallet after rotating the cam so the valve will move when smacked.

The third thing to look for is breakage at the top of the pistons above the compression ring. This is fairly common but usually allows the engien to start run and drive albiet with out the power it should be developing.

There are really no drop in engine swaps as each one brings with it ist own set of changes, compromises and work arounds. The flat heads aren't a high erformanc engine by any means, but one in proper mechanical condition can provide miles of reliable and entertaining driving. I have driven mine on numerous 400+ mile trips with the only issue being a thrown fan belt.

In the picture below the arrow on Number 6 piston points to the narrow section between the piston pairs where had gaskets typically fail.

[rayosequis]

Thanks for the quick responses ! The cylinders are not adjoining, unfortunately, they would be, from radiator, the 2nd and 6th cylinders. I will definitely pull the head and see if the valves are sticking. Hopefully it is something simple.

We did not get as far as taking actual compression readings as we literally had zero compression on the two cylinders in question. I had filled the cylinders with tranny fluid and then seafoam to try and help loosen things up as the car has been sitting for ~15 years. It did make a noticeable difference on several of the cylinders.

Is there a torque spec/sequence for the head posted anywhere on the site ?

Thanks again,

Ernie

Edited June 11, 2012 by rayosequis

[greg g]

Use the return to P15 D 24 button on the upper navigation banner. It will take you to the host sight for this forum with a lot of good info. Torque is 65 to 70 lb ft. and the sequence is a star pattern moving out from the center and working towards the ends. A retorque is required after a heat cycle. There should be a petcock or plug on the block down between the oil fill and dist to allow the block to be drained of coolant.

typicle sequence, starting from the center;

9, 3, 5

7, 1, 4

8, 2, 6 etc.

Edited June 11, 2012 by greg g

[rayosequis]

On a side note, my brother does have a straight 6 from a Chevy that was recently rebuilt that I could get for little to nothing.

Thanks for the info, greg_g !

[greg g]

The chevy engine is at least 2 or 3 inches longer than the MOPAR so a radiator reposition is the minimum required, plus the exhaust and intake are on opposite sides and the transmission mount is quite different not to mention the linkage. As would be the driveshaft and you would loose the emergency brake. None of these things are impossible to overcome but you can see the line in the sand move with every item.

Oh by the way your car is likely equiped with fluid drive. This means that there is no mechanical connection between the engine and drive line(no compression braking with engine off) so a working parking brake and or wheel chocks are a must to keep you car from visiting neighbors unless it's parked on a dead level.

[Rusty O'Toole]

Best and easiest is to repair, overhaul or rebuild your motor. They are simple, parts are available and not very expensive. When they are in good shape they turn in a good performance on the road, although hardly a race car.

If you are curious look up Jay Leno's web site and his 1941 Plymouth coupe. He takes it out on the road and discusses its performance merits and demerits. What he says would apply with equal force to your car.

There is no other motor that will fit your car. The bigger flathead six from a DeSoto or Chrysler will squeeze in but any V8 has serious interference with steering and requires replacing the transmission and rear axle as well. Much better and easier and cheaper to fix the motor you have. They are a good old motor, if the rod is not sticking through the block and the block is not frozen and cracked it should be possible to put it back in commission.

Edited June 11, 2012 by Rusty O'Toole

[moparbenny]

http://www430.pair.com/p15d24/mopar_forum/album.php?albumid=36&pictureid=470

just go with a 440:cool:...but it's not easier and it's not cheaper...i'm in a street rod club..my dad was a street rodder..there are a lot of them that think that rebuilding the org. engine is more $$$..but it's not..because you change to a v8 then you got change tranny$..then drive shaft.$.then rear end.$..(8 3/4 out of a c body with work..we got one out of a 71 polara)..plus when you change to a v8 you want to make it look like it was so pose to be there..which takes some thinking..plus you can only go as fast as the signs tell you to go...unless building a bracket racer?..which would be cool!

a lot of people in my club give me bad time for not wanting to rod my '33..but

i added up the cost to rod or restore..restoring is cheaper because i can do all the work my self..and farm out very little..i just tell people the '33 was built to be driven 12 months out of the year..i just want to drive it 3.

when dad got his d24 the flatty was tired and his best friend ( who's a really good bodyman and rod builder).."why don't you just put that 440 you have for the '33 in the '48?"..so that's what happened...of cource the best friend that knew what he was doing ended up doing all the work..of cource the '48 got a '77 camero clip...etc...

if it been me i was have just put another flatty in it..saved a lot of time and money..these mopar flatheads are not like the ford flatheads were everything costs so much..the parts are really cheap..

then again there's nothing like the feeling of driving a 440 powered d24:cool: just my 2 cents..benny

Edited June 11, 2012 by moparbenny

[Rusty O'Toole]

You can put in a 440 motor if you want. But you will also have to replace the transmission, drive shaft and the rear axle. Of course the original steering will have to go as it is in the road. And you will need new front suspension with disc brakes to handle the extra power. New wheels and tires of course.

While you are at it don't forget the new radiator, and Oh ya you will have to rewire the car and replace everything in the electrical system to convert to 12 volts.

A good hot rod shop should be able to do the whole job for you, for around $50,000.

Or, you could just go buy a car that came with a V8 and save all that work and expense.

[rayosequis]

Thanks for the replies guys, I do appreciate the advice. It of course boils down to the old adage of you do anything you want if you have enough talent or money.

I wasn't really too sure about the V8 conversion, as this car is a cruiser not a hot rod, but I thought it was an avenue worth exploring nonetheless. It does seem like that is going to be more work than I am looking to tackle with this car.

I am hoping to salvage the flat head, so wish me luck !!

-Ernie

[moparbenny]

Thanks for the replies guys, I do appreciate the advice. It of course boils down to the old adage of you do anything you want if you have enough talent or money.

I wasn't really too sure about the V8 conversion, as this car is a cruiser not a hot rod, but I thought it was an avenue worth exploring nonetheless. It does seem like that is going to be more work than I am looking to tackle with this car.

I am hoping to salvage the flat head, so wish me luck !!

-Ernie

luck:) hope i didnt discourge you..i have just been at the same point many times before..i have learn from what my dad has done..and your right it comes back to talent and money..and how much of those do you really have?..good luck benny..p.s ..you don't have to go disc brakes if you don't want too. you can get a 67 ford(mustang) mastercylinder..duel chamber..(for drum/drum) then put the power buster on...and it with stop on a dime:)

[Frank Elder]

On a side note, my brother does have a straight 6 from a Chevy that was recently rebuilt that I could get for little to nothing.

Thanks for the info, greg_g !

Find a chevy car for it to go in.........good luck with your flathead.